The invention relates to an electrically insulated pipe joint comprising a first metal tubular part having at one end a flange and a second metal tubular part which is coupled to the first tubular part by a metal coupling sleeve surrounding the flange and narrowing behind the flange, wherein between both tubular parts and between the coupling sleeve and the first tubular part an electrical insulation is disposed.
Such a pipe joint is known from Dutch patent application No. 6709100 now U.S. Pat. No. 150,895 which corresponds to U.S. Pat. No. 3,441,293. In this known pipe joint the coupling sleeve consists of a bell which is formed at the end of the second tubular part facing the end of the first tubular part. Between the front surface of the flange and the bottom of the bell an insulating seal ring is disposed, and at the rear side of the flange a conical insulating sleeve surrounding the first tubular part is disposed between the inner side of the bell and the first tubular part. Thereby the metal parts of both tubular parts at any location are separated from each other by a single insulation only so that a breaking down of the insulation when, for example, struck by lightning, renders the insulating pipe joint ineffective. When the outer surface of the bell were in contact with other metal or masonry structures, furthermore the pipe line which is electrically connected with the bell would be grounded through this contact.